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A&P Lecture 2
A&P Lecture 2 Week 2
| Term | Definition |
|---|---|
| Skin is | the most vulnerable organ - Exposed to radiation, trauma, infection, and chemicals - Received more medical treatment than any other organ system - has 2 layers |
| Dermatology: | scientific study and medical treatment of integumentary system |
| The integumentary system: | consists of skin, hair, nails, and associated glans The skin (integument) is the body's largest and heaviest organ Covers area 1.5 to 2.0 m^2 Composes 85 of body weight |
| Epidermis: | stratified squamous epithelium |
| Dermis | : deeper connective tissue layer - Below the dermis is the hypodermis, not part of the skin but usually studied with it |
| Skin thickness ranges from | 0 .5-6 mm - Thickness range mainly due to variation in dermis thickness, but skin is classified as thick or thin based on the epidermis |
| Thick skin: | covers palms, soles, and corresponding surfaces of fingers and toes Has sweat glands, but no hair follicles or sebaceous (oil) glands Epidermis about 0.5 mm thick, primarily due to thick stratum corneum Epidermis thick skin: BSGLC (palms, soles) |
| Thin Skin: | covers rest of the body Has hair follicles, sebaceous glands, and sweat glands Epidermis about 0.1 mm thick Epidermis thin skin: BSGC (everywhere else) |
| Arrector pili muscle: | red tube attached to purple L shaped figure (hair follicle) in the skin's dermis, attached to hair follicles and the overlying epidermis (involuntary response) causes hairs to stand on end, creating "goosebumps" through a process called piloerection |
| Functions of the skin: | Resistance to trauma/ infection - Keratin: provides physical protection - Dermcidin, defensins, and acid mantle protect against bacteria Barrier to water, ultraviolet (UV) rays, harmful chemicals Vitamin D synthesis - Skin carries out first step |
| other functions of the skin | Sensation - Many nerve endings that react to various stimuli Thermoregulation - Alter blood flow to release or retain heat - Cutaneous vasoconstriction,cutaneous vasodilation Nonverbal communication - Facial expressions |
| General features of the epidermis: | Keratinized stratified squamous epithelium - Includes dead cells ay skin surface packed with tough keratin protein - Avascular - Depends on diffusion of nutrients from underlying ct - Contains sparse nerve endings for touch and pain |
| Avascular | (lacks blood vessels) |
| Five epidermal cell types: | Keratinocytes, stem cells, melanocytes, tactile/merkel cells, dendritic cells |
| Keratinocytes | (cytes mature cell doing its thing) Great majority of epidermal cells Synthesizes keratin |
| Stem cells | Undifferentiated cells that give rise to keratinocytes In deepest layer of epidermis, stratum basale |
| melanocytes | Synthesize pigment melanin that shields the DNA from ultraviolet radiation Occur only in stratum basale but have branched processes that spread among keratinocytes and distribute melanin via melanosomes |
| Tactile (merkel) cell | Tough receptor cells associated with dermal nerve fibers tactile disc In the stratum basal layer of epidermis |
| Tactile disc: | a collective term for tactile cell and associated nerve fiber |
| Dendritic cells: | Phagocytic immune cells that guard against toxins, microbes Found in stratum spinosum and stratum granulosum |
| Free Nerve Endings: | yellow nerve like structures in the epidermis/dermis unencapsulated sensory receptors in the skin that detect pain, temperature, itch, and light touch |
| Layers of the epidermis: | cells of the epidermis are arranged in four to five zones, or strata, listed here from superficial to deep |
| Stratum basale: | a single layer of stem cells and keratinocytes resting on the basement membrane - stem cells goes through mitosis Also contains scattered melanocytes and tactile cells |
| Stratum spinosum: | several layers of living keratinocytes joined by desmosomes & tight junctions Creates keratin & deposits it within itself Looks spiny w tiny needles, keratin is visible contains dendritic cells |
| Stratum granulosum: | Three to five layers of flat, living keratinocytes Cells contain dark-staining keratohyalin granules |
| Stratum lucidum: | Thin, pale layer found only in thick skin (found on palm and soles) Keratinocytes pack with clear protein called eleidin |
| Stratum corneum: | Up to 30 layers of dead, scaly, keratinized cells Held by tight junctions, full of keratin, and releases lipids that gets stuck - which prevents water loss resists abrasion and penetration |
| Dermis general features: (mostly collagen) | Connective tissue layer 0.2-4mm thick mainly collagen; also elastic & reticular fibers Well supplied w blood vessels, sweat/sebaceous glands, nerve endings Houses hair follicles & nail roots Wavy, conspicuous boundary |
| Dermal papillae: | are upward, finger-like extensions of dermis bumps on top of the dermis, extensions of the dermis: are upward, finger-like extensions of the dermis |
| Epidermal ridges: | are downward waves of epidermis |
| The dermis consists of two zones: | papillary layer and reticular layer |
| Papillary layer: | Thin zone of areolar tissue in and near the dermal papillae Allows for mobility of leukocytes and other defense cells Rich in small blood vessels |
| Reticular layer | deeper, thicker layer of dermis Composed of dense irregular connective tissue - makes skin stretchy and strong |
| Stretch marks (striae) - | tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity |
| The hypodermis (subcutaneous tissue) - | layer of connective tissue beneath the skin Contains more areolar and adipose tissue than the dermis Pads the body and binds skin to underlying tissues Common site of drug injection due to many blood vessels |
| Subcutaneous fat: | refers to subcutaneous tissue that is comprised predominantly of adipose tissue Energy reservoir Thermal insulation Thicker in women Thinner in infants, elderly |
| Damaged dermal blood vessels (burns, shoe friction) may cause | serous fluid to seep out and form a blister between the dermis and epidermis |
| Lamellated Corpuscle: | green lined oval shaped figure attached to yellow cloud figure in (dermis and hypodermis), loose connective tissue throughout body. responsible for sensing deep pressure, high-frequency vibrations by responding to sudden, transient disturbances. |
| Skin color: | variations in skin and hair color due primarily to type and amount of melanin pigment |
| Eumelanin | : varieties: brown and black eumelanin; responsible for tan, brown, and blak skin |
| Pheomelanin: | responsible for yellowish to reddish tones in some asians and native americans, and pinkish tones of white skin |
| Other contributing factors to skin color | Degree of show-through of dermal vessels and white collagen Possible accumulation of carotene pigment from yellow and orange vegetables UV radiation, which stimulates melanin synthesis |
| People of different color have same number of melanocytes, but vary in | melanin production and longevity |
| Darker skin: | Melanocytes produce greater qualities of melanin Melanin breaks down more slowly Melanin granules more spread out in keratinocytes Melanized cells seen throughout the epidermis |
| Cyanosis: | blueness due to oxygen deficiency If darker skin tone can see their gum line and nailbeds |
| Erythema: | redness due to increased blood flow to skin If darker skin can feel for heat and red patches |
| Pallor: | paleness due to decreased blood flow to skin |
| Albinism: | white skin due to genetic lack of melanin |
| Jaundice: | yellowing due to bilirubin in blood Can be caused by compromised liver function |
| Hematoma: | bruising Clotted blood under skin |
| Friction ridges: | Markings on fingertips that leave oily fingerprints Everyone has a unique pattern formed during delta development that remains unchanged; not even identical twins have identical fingerprints Enhance fingertip sensitivity; improves grip |
| Flexion lines (flexion creases) | Lines on the flexor surfaces of the digits, palms, wrists, elbows Mark sites where skin folds during flexion of joints Skin bound to deeper tissues along these lines |
| Freckle: | flat, melanized patch |
| Mole (nevus): | elevated, melanized patch, often with hair Should be watched for changes in color, diameter, or contour that may suggest cancer |
| Hemangiomas (birthmarks) | Patches of discolored skin caused by benign tumors of dermal capillaries Some disappear in childhood, others last for life Examples: capillary hemangioma (strawberry birthmark) cavernous hemangioma, port-wine stain |
| Hair, nails, and cutaneous glands are the accessory organs (appendages) of the skin | Hair and nails are composed of mostly dead, keratinized cells Pliable soft keratin makes up stratum corneum of skin Compact hard keratin makes up hair and nails Tougher and more compact due to numerous disulfide bridges between keratin molecules |
| A hair is also called a | pilus (plural: pili) |
| Hair follicle: | A slender filament of keratinized cells growing from a tube in the skin Hair covers most of the body |
| Hair does not cover: | palms, soles; palmar, plantar, and lateral surfaces and distal segments of fingers and toes; lips, nipples, and parts of genitals |
| Limbs and trunk have | 55 to 70 hairs per square cm; face has about 10 times as many 100,000 hairs on an average person’s scalp Difference in hairiness across individuals mainly due to differences in texture and pigment of hair |
| hair Shaft: | is the portion the hair above skin surface |
| hair Root | is the portion of the hair below the skin surface In dermis or hypodermis, hair root ends with dilated bulb |
| Bulb grows around dermal papillae: | a bud of vascular connective tissue, provide nutrition to hair |
| Hair matrix: | mitotically active cells immediately above the papilla; growth center for the hair |
| Hair has three layers: | medulla, cortex, and cuticle |
| medulla : | central core of the hair strand - center core of loosely arranged cells and air spaces - in gray hair it is hollow |
| Cortex: | bulk of the hair; layers of elongated cells - gives the hair its color and strength |
| Cuticle: | outermost region consisting of multiple layers of thin, scaly cells that overlap like root shingles |
| Color due to pigment granules in the cells of the cortex: (due to melanin pigment in hair) | Brown/black hair is rich in eumelanin Red hair: high concentration of pheomelanin, very little eumelanin Blonde hair: intermediate amount of pheomelanin, very little eumelanin Gray/white hair have little/no melanin; are present in the medulla |
| Texture related to cross-sectional shape of hair | Straight hair is round Wavy hair is oval Curly hair is relatively flat |
| Hair functions: | Hair receptors alert us of parasites crawling on skin Hair on trunk and limbs is mostly vestigial Scalp hair retains heat and protects against sunburn Eyelashes and eyebrows enhance facial expression and non verbal communication |
| Guard hairs (vibrissae) | guard nostrils and ear canals |
| Pubixc and axillary hair - | signify sexual maturity and aid in transmission of sexual scents |
| Fingernails and toenails: | clear, hard derivatives of stratum corneum Composed of thin, dead cells packed with hard keratin |
| Nail functions: | Improve grooming, picking apart food, other manipulations Provide a counterforce to enhance sensitivity of fleshy fingertips to tiny objects |
| Nail plate: | hard part of nail; include overhanging |
| Free edge, | nail body (visible attached part, |
| nail root: | under overlying skin Surrounding skin rises as a nail fold, separated from the margin of the nail plate by the nail groove |
| Two kinds of sweat glands: | apocrine and eccrine |
| Apocrine sweat glands: | associated w hair follicles, coarse hair Groin, anal region, axillia, areola, beard area Ducts lead to nearby hair follicles, produce sweat that is milky, contains fatty acids - lead to funky smell |
| eccrine/merocrine sweat glands: (nervous sweats) - | mostly simple cuboidal Most numerous skin glands - 3-4 million in adult skin, especially dense on palms, soles, and forehead Simple tubular glands produce water perspiration that helps cool the body |
| apocrine sweat glands are | Inactive until puberty; respond to stress and sexual stimulation Believed to secrete sex pheromones: chemicals that can influence behavior of others |
| Sweat glands are production and composition: | 99% water pH range of 4-6 Begins as a protein-free filtrate of blood plasma produced by deep secretory portion of gland Most fluids are derived from the blood and return to it Some drugs are excreted in sweat |
| Acid mantle: | inhibits bacterial growth |
| Sebaceous gland: | Produces oily secretion (sebum) Gland structures: flask-shaped, short ducts into hair follicles Keeps skin and hair from becoming dry, brittle, and cracked |
| Sebum: | oily secretion |
| Ceruminous glands: | modified apocrine glands found only in external ear canal Excrete a waxy type substance - cholesterol based Produce cerumen (earwax) Coiled, simple tubular glands |
| Creumen: | ear wax, yellow, waxy secretion combined with sebum and dead epithelial cells Keeps eardrum pliable Waterproofs the canal Makes guard hairs of ear sticky to help block foreign particles from entering auditory canal Kills bacteria |
| Mammary glands: | milk-producing glands that develop in females during pregnancy and lactation Modified apocrine sweat glands Embedded in the epidermis Rich secretion released through ducts opening at nipple |
| Mammary ridges or milk lines: | two rows of mammary glands in most mammals Primates kept only two glands, but a few people have additional nipples along the milk line (polythelia) |
| Cutaneous glands: | glands located in the skin, also known as skin glands, which secrete substances to the outside of the body to maintain skin health and regulate body temperature |
| Thick skin vs Thin skin | Thick skin is BSGLC, thin skin is BSGC no stratum lucidum which only to thick skin palms/soles |
| Wrinkles and stretch marks are visible on the surface and are just reflecting things from what layer of the skin? | dermis |
| Which layers of the epidermis are considered to be alive, before they start dying? | Basale and spinosum are alive, granulosum is in apoptosis, while lucidum and corneum are dead |
Created by:
Katepop10